Many types of vehicles, and particularly tractors, are operative in a number of different modes, which require different orientation of their wheels.
The present inventor has appreciated that tractors should be designed to have a relatively wide wheelbase in order to enable them to carry out a given function over a field in a minimum of transversals, thereby saving time and fuel and reducing the damage to crops due to traversal of the tractor as well as reducing the number of tractor traversable separations between crops. Further advantages, such as non-interference with irrigation conduits and the like, may also be appreciated.
A concomitant requirement in the design of a tractor is that it be capable of self-propulsion over the highway transport. It may be appreciated that, due to its wheelbase, a tractor of the design described hereinabove could not travel along a highway of the same wheelbase. It is thus necessary to orient the tractor along a narrower profile for highway transport.
A further important design principle requires that a tractor be capable of a 180 degree turn about a pivot axis defined by one of its wheels, so as to enable the tractor to turn at the end of a row and return along an adjacent row with the pivot wheel in the same channel.
An additional principle of design requires that a tractor be capable of a full turn about a pivot axis defined by its geometric center, or by the mid-point of an imaginary line joining two wheels along the narrower wheelbase.
A further important design feature of tractors is that of efficient power transmission for agricultural machinery connected thereto and powered thereby. A measure of power required by machinery is the number of Revolutions Per Minute (RPM) of its motor or of other similar motive apparatus.
With machinery powered by the Power Take Off (PTO) of a conventional tractor, it is usual, that in order to obtain a high number of RPM at the PTO, through which power is transferred to connected machinery, the tractor engine is also required to revolve at the same rate of RPM, this being particularly wasteful of fuel.